The Wu & Palmer measure calculates relatedness by considering the depths of the two concepts in the UMLS, along with the depth of the LCS. The formula is score = 2*depth(lcs) / (depth(s1) + depth(s2)). This means that 0 < score <= 1. The score can never be zero because the depth of the LCS is never zero (the depth of the root of a taxonomy is one). The score is one if the two input concepts are the same.

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